This invention relates to current sensors used in electrical switchgear.
Current sensors are used in the electric power industry to measure current flowing in electrical systems. In particular, current sensors may be used in electrical switchgear such as circuit breakers, reclosers, and switches to determine when a fault has occurred in the electrical system.
In one general aspect, an electrical switchgear device includes a conductor, a base, and a current sensor positioned to detect current in the conductor and attached to the base using a support element. The device also includes an apparatus mounted to the base to interrupt current through the conductor when a signal from the current sensor indicates a predetermined condition. A housing positioned on the base encapsulates the current sensor, the support element, the current interrupting apparatus, and the conductor.
Embodiments may include one or more of the following features. The housing may include a solid insulating material. The support element may include a rigid tube. The support element may be bent at an end coupled to the current sensor. The bent end of the support element may include a support strip shaped to match a curvature of the current sensor.
The current sensor may include a sensor conductor that produces a signal. The support element may be hollowxe2x80x94in this case, the sensor conductor is drawn through the support element to control circuitry. The sensor conductor and the support element may be hermetically sealed. The support element may be hermetically sealed to the base.
The support element may be metallic or non-metallic. In either case, the support element may be coated with a semi-conductive paint.
The housing may encapsulate the current sensor, the support element, the current interrupting apparatus, and the conductor such that there is no dielectric interface between the current sensor and the conductor.
In another general aspect, a method of producing an electrical switchgear device includes securing a support element to a current sensor. The current sensor is mounted relative to a main conductor by securing the support element to a surface of a mold that houses a current interrupter and a portion of the conductor. A prepared material is injected into the mold to encapsulate the support element, the current sensor, the conductor, and the current interrupter. The injected material is permitted to solidify to form a housing.
Embodiments may include one or more of the following features. The support element may be secured to the current sensor by drawing sensor conductors from the current sensor through a hollow passage of the support element. The support element may be secured to the current sensor by bending a first end of the support element and attaching to the first end a support strip shaped to match a curvature of the current sensor. The support element may be secured to the current sensor by securing the support strip to the current sensor.
The support element may be secured to the surface of the mold by connecting a second end of the support element to a post positioned at the surface of the mold. The second end of the support element may be connected to the post by hermetically sealing the second end to the post. The second end of the support element may be connected to the post by drawing sensor conductors from the current sensor through a hollow passage of the post. The method may include removing the mold from the housing and securing the housing to a tank that houses additional components.
The electrical switchgear exhibits improved overall dielectric performance because all of the components are encased into a single housing with no dielectric interfaces. Moreover, the electrical switchgear exhibits a longer life because of reduced failure associated with dielectric breakdown at interfaces. Manufacturing of the electrical switchgear is more economical due to simplification of the current sensor design.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description, the drawings, and the claims.